Emulsion polymerization of unsaturated organic compounds



Patented Oct. 2, 1951 UNITED STATES PATENT OFFICE EMULSIONPOLYMERIZATION OF UNSAT U- RATED ORGANIC COMPOUNDS Eugene J. Lorand,Wilmington, Del., assignor to Hercules Powder Company, Wilmington, Del.,7 a corporation of Delaware Serial No. 656,539

No Drawing. Application March 22, 1946,

nique synthetic rubberlike materials have been prepared by polymerizingdioleflns, halogen derivatives of diolefins or'other substituteddioleflns or by interpolymerizing diolefins with other compoundscontaining a vinyl group such as styrene, acrylic acid esters, andacrylic acid nitrile. Polymers such as polyvinyl halides,polyvinyl-acetatemolys wrene, polymethyl methacryl ate, and variousother addition polymers also have been prepared by polymerization inaqueous emulsion. Soaps of fatty acids commonly have been used asemulsifying agents for polymerizations of .this type;

These polymerizations usually have been carried out using a peroxidecatalyst such as potas- 12 clai 21. 260-823) In carrying out the thisinvention the polymerization of vinyl, vinylidene, and vinylenecompounds is efiected in the usual manner utilizing the well-knownemulsion technique with the exception that the catalyst utilizedconstitutes an aryl(dialkyl)methyl hydroperoxide. The catalyst used inaccordance with this irflention permits polymerizations at lowertemperatures and shorter reaction times, and results in higher yields.

' The following examples are illustrative of the preparation of polymersby emulsion polymer:

- ization and the products thereof in accordance with this invention.All parts given in the examples represent parts by weight.

Example I A glass polymerization vessel was charged with 41.7 parts of a6% solution of the sodium salt of a dehydrogenated rosin (dehydroabieticacid,

53%; abietic acid, 0.0%; retene,-0.2%), this solusium persulfate,benzoyl peroxide, tert-butyl hydroperoxide, and the-like. Thesecatalysts have been quite useful in polymerizations of this type buthave had one marked disadvantage in that they have necessitated too longa reaction period at moderate temperatures in order to obtain areasonable yield of the polymeric materials. Furthermore, unreasonablelengths of time have been necessary to obtain optimum yields. The longreaction period usually associated with .the use of these catalysts hasbeen shortened by using increased temperatures during thepolymerizations, but the resulting polymers have suffered through use ofsuch temperatures. Synthetic rubberlike materials, for example, havesuperior 'physical properties when they are prepared by low temperaturepolymerization. Until recently, however, it has been impossible from thestandpoint of'yield to combine the desirable features of low temperaturepolymerization and a relatively short reaction period. Furthermore,under the conditions generally used in synthetic rubber production, ithas not been possible to effect a more optimum yield.

Now in accordance with this invention, it has been. found that thepolymerization of organic compounds containing the CH2=C group and'whlch are capable of being polymerized by a peroxide catalyst maybecarried out to advantage in aqueous emulsion in the presence of anmuamkyo methyl hydroperoxide.

' sulting solution was frozen prior to the addition tion containing 2.5parts of the sodium salt of the dehydrogenated rosin. To this soapsolution were added 0.0478 part of a,a-dimethyl-p-isopropylbenzylhydroperoxide, 49.88 parts of water and 1.00 part of an activating saltsolution. The 1.00

part of activating salt solution contained 0.00525 part of 78% ferricsulfate nonahydrate, 0.075 part of sodium pyrophosphate decahydrate, and0.00019 part of cobaltous chloride hexahydrate dissolved in 0.92 part ofdistilled water. The reof 12.5 parts of styrene, 0.25 part of laurylmercaptan, and 37.5 parts of butadiene-1,3 to the polymerization vessel.The mixture was agitated at 50 C. for 14 hours in the sealedpolymerization vessel. The emulsion was then run into an openvesselcontaining 5 parts of a 2% solution of phenyl fl-naphthylamine,stripped of the excess butadieneand the polymer precipitated by theaddition of an excess of a saturated salt solution.

The precipitated polymer was washed with water until alkali-free, then.with 'alcohol, and finally was dried in an oven. A yield of 100%polymer was obtained.

Example II.

The procedure of Example I was followed with I the exceptions that noactivating salt solution was used and the amount of hydroperoxide was0.0955. The yield of polymer was 74%.

Example III 'The process of Example I was duplicated with ried out for 8hours. A 75% yield of polymer was obtained.

process in accordance with aseaao Example IV Fifty parts of methylmethacrylate was polymerized according to the procedure shown in ExampleI with the exceptions that 0.0911 part of a,a-dimethyl-p-methylbenzyl.hydroperoxide was utilized as the catalyst and the polymerization wascarried out over a temperature range of 82 C. to 98 C. for a period of 4hours. An 86% yield of polymethyl methacrylate was obtained.

Example V A glass polymerization vessel was charged with 41.7 parts ofthe emulsifying solution shown in Example I. To this solution were added0.0841

part of a,a-dimethylbenzyl hydroperoxide, 49.88.

parts of water, 1.00 part of the activating salt solution of Example I,0.25 part of lauryl mercaptan, and 50 parts of styrene at a temperatureof 25 C., the vessel sealed, and its contents frozen by cooling. Thevessel then was opened and the free space thoroughly swept out with air,resulting in the introduction of 0.025 part of oxygen, based on thestyrene, after. which the vessel again was sealed and the reactionmixture agitated at 40 C. for 16 hours. Upon working up the reactionmixture as in Example I, a 93.8% yield of polystyrene was obtained.

Example VII Twelve and one-half parts of styrene and 37.5 parts ofisoprene were copolymerized according to the process of Example VI overa period of 48 hours, resulting in an 80.6% yield of. polymer.

Example VIII The procedure of Example VI was duplicated with thesubstitution of 50 parts of butadiene- 1,3 for the styrene previouslyshown. A 96.4% yield of polymer was obtained.

Example IX Twelve and one-half'parts of acrylonitrile and 37.5 parts ofbutadiene-l,3 were copolymerized following the process of Example VIwith the exception that the polymerization was carried out for 18 hours.A 100% yield of polymer was obtained.

A Example X Twelve and one-half parts of styrene and 37.5

parts of butadiene-1,3 were copolymerized'am in which R1 and Rirepresentalkyl groups and Ar represents a substituent selected from the groupconsisting of aryl and substituted aryl groups. The oxidation maybecarried out in the liquid phase utilizing air or molecular oxygen as theoxidizing agents A preferred method of preparing these hydroperoxidesinvolves the liquid phase oxidation of the alkyl-substituted aromaticorganic compounds having the above structural formula by passing anoxygen-containing gas through the compounds at a temperature betweenabout 25 C. and about 95 C. in the presence of an aqueous alkali. Theconcentration of the aqueous alkali may be between about 1% and about35% although it is preferable to use concentrations of about 2% to about8%. Vigorous agitation is desirable during the oxidation reaction.

As illustrative of the alkyl-substituted aromatic organic compoundswhich may be oxidized, p-cymene, cumene, and diisopropyl benzene may bementioned. These compounds lead to e,e-dimethyl-p-methylbenzyl,u,a-dimethylbenzyl, and a,a.- dimethyl-p-isopropylbenzyl hydroperoxides,respectively. These compounds also may be named as aryl(dialkyl)methylhydroperoxides;

for example, a,a-dimethylbenzyl hydroperoxide may be designated asphenyl(dimethyl)methyl hydroperoxide. The aryl and substituted arylgroups need not be derived from benzene, as is the case in theaforementioned compounds, for compounds containing aromatic nucleiderived from naphthalene, anthracene, phenanthrene, and the like alsoare operable when dissolved in a suitable solvent during the oxidation.The aryl group may be substituted with alkyl groups such as methyl,ethyl. propyl, isopropyl, butyl, isobutyl, tertiary butyl, and the like,the same alkyl groups.also being representative of R1 and R2 in thestructural formula. R1 and R2 may be either the same or different.

The amount of hydroperoxide which may be used in accordance with thisinvention may be between about 2% and about 9% based on the amount ofsolid emulsifying agent used. The preferable amount of hydroperoxide onthis basis, however, is from about 2% to about 5%.

The process of this invention may be carried out using various.emulsifying agents, such as fatty acid soaps; the water-soluble salts ofhydrogenated and dehydrogenated rosins or the pure acids thereof, suchas dihydroabietic, tetrahydroabietic and ,dehydroabietic acids; thewater-soluble salts of the amines derived from hydrogenated anddehydrogenated rosins or the pure acids thereof, for example, theacetates of dihydroabietylamine, tetrahydroabietylamine, anddehydroabietylamine} and any other emulsifying agent wellknownin theart. The rosin amines mentioned may be prepared by converting the acidsin the rosin material to the corresponding nitriles by treatment withammonia under dehydrating conditions, and then reducing the nitriles tothe amines by catalytic hydrogenation.

Most of the examples, however, have shown the use of a salt ofdehydrogenated rosin as emulsifying agent. Such saltsare prepared .byneutralization of a dehydrogenated rosin with an alkali metal compoundbasic in characteristics, such as the hydroxides and carbonates ofsodium and potassium. The dehydrogenated rosins are prepared by thedehydrogenation or disproportionation ofnatural rosin or a rosinmaterial containing a substantial amount of a natural tion reaction iscarried out by contacting the rosin or rosin material at an elevatedtemperature with an active hydrogenation catalyst in the absence ofadded hydrogen. Catalysts such as palladium, platinum, nickel. andcopper chromite are suitable and may be supported on a carrier such asgranular alumina, fibrous asbestos or activated charcoal. The catalytictreatment may be conducted either by a batchwise or continuousprocedure. The rosin may be agitated, for example, with about to aboutby weight of a palladium catalyst supported on activated carbon (1% to2%, palladium) at about 150 C. to about 300 C. forabout 1 hour to about5 hours. In the continuous process the molten rosin flows over thesupported palladium catalyst at atomperature within the range or about225 C. to

about 300 C. to provide a contact time of about A hour to about 1 hour.

It often is advantageous to refine the whole rosin prior to itsdehydrogenation or dispropor tionation and the same is true as appliedto the whole dehydrogenated or disproportionated prod-- uct. Prior toits dehydrogenation or disproportionation the rosin may be refinedbycrystallization, by means of a selective solvent such as furfural 0rphenol, or by an absorbent earth such as fullers earth. Thedehydrogenated or disproportionated rosin product may be refined by.dis-

tillation, heat-treatment, alkali .extraction, precipitation, etc. It isdesirable that the dehydrogenated or disproportionated rosin orderivative thereof contain at least and preferably at leastdehydroabietic acid.- The dehydrogenated or disproportionated rosin alsoshould contain less than 1 abietic acid.

As shown bythe examples various activating salts may be added to thepolymerization reaction mixture. The activating salts shown by theexamples; namely, ferric sulfate, sodium pyrophosphate, and cobaltouschloride,'constitute a vredox system, which is so called because of itsproperty of catalyzing oxidation-reduction reactions. Such systemsusually comprise a salt of a heavy metal such as iron, cobalt orn'ickelasso ciated with a complex-forming compound such as a pyrophosphate. Theredox system, therefore, comprises essentially a heavy metal complexwherein the metal isunited to another element through coordinatecovalences rather than primary valences. Amounts between about 0.1% andabout 1% by weight of the heavy metal complexes based on the monomerspresent are generally suitable. The salts of some heavy metals such asiron are sufiiciently active so that the salt of .only one metal need bepresent, but usually the redox system contains at least two heavy metalsalts, and each individual salt may be present in the redox system inamounts the use of these soaps has been somewhat disadbetween about0.0003% and about 0.01% by weight based on the monomers employed.

Compounds which may be advantageously polymerized in aqueous emulsioninaccordance with this invention include the conjugated butadienehydrocarbons, butadiene, and itsv derivatives such as isoprene, dimethylbutadiene,

chloroprene, etc., and other compounds containing the vinyl group suchas styrene, acrylonitrile, etc. Through utilization of the hydroperoxidecatalysts, particularly advantageous results have been obtained in thepreparation of copolymers of butadiene and styrene -or acrylonitrile,isoprene and styrene or acrylonitrile and other rubin which each alkylgroup contains not more than alent to those obtained with fatty berlikecopolymersas -well as in-the preparation. of polymers .such aspolystyrene, polymethyl- 'methacrylate, and the various other additionpolymers which may be technique;

Thepolymerizations may be carried out under conditions well known in theart. for emulsion polymerization; e. g., concentrationof reactants.temperature, pressure, etc. The temperature of the polymerizationreaction may vary from about 20 C. to about -C. and the concentration ofthe emulsifying agent in the aqueous phase may be varied from about 1%to about 5%, preferably fromabout 2% to about 3%. During thepolymerizations; it is desirable that a modifier, such as laurylmercaptan, bepres'ent in the reaction mixture.

As illustrated in Examples VI to X, the addition of oxygen, in the formof vair in these examples, has a beneficial effect on polymer yieldsobtained when using an ar yl(dialkyl)- methyl hydroperoxide as acatalyst. In Examples VI to IX the amount of oxygen was 0.05 part per100 parts of monomers, and in Example X on the same basis it was 0.12,but an amount of oxygen up to about 0.4 part per 100 parts of monomersis beneficial.

The. aryl(dialkyl) methyl hydroperoxide 'cata- I lysts of this inventionpermit a higher yield of polymer under the same conditionsthan do thecatalysts previously used in the art. The present catalysts areadvantageousin that the time required to obtain a given yield of polymeris reduced, as compared to previous processes, thereby increasing thecapacity of a polymerization vessel and decreasing the cost of apolymer. Furthermore, :through'practice of this invention increasedyieldsare obtained by polymerizations ca'rried out at lower temperaturesfor periods of time comparable to those which .have previously J beenused in the art. The use ofthe catalysts of this invention in 'thepreparation of rubberlike soaps impart'desirable physical properties torubberlike polymers, such as those derived from the copolymerization ofbutadiene and styrene, but

vantageous due to the fact that there existed a rather long period ofslow reaction during 'the initial phases of the polymerization. Thecatalysts of this invention permit the use of dehydrogenated rosin soaps,to obtain in comparable lengths of time polymer yields which areequivacid soaps using persulfate catalysts.

What I claim and desire to protect by Letters Patent is:

1. The process which comprises polymerizing an organic compoundcontaining the CH2=C group and which is capable of being polymerized bya peroxide catalyst, in aqueous emulsion in the presence of an'aryl(dialkyl)methyl hydroperoxide in which each alkyl group containsnot more than 4 carbon atoms.

2 The process which comprises polymerizing an organic compoundcontaining the CH =C group and which iscapable of being polymerized by aperoxide catalyst. in aqueous emulsion in the presence of anaryl(dialkyl) methyl hydroperoxide prepared by the emulsion.

assasso 4 carbon atoms, and an activator comprising a water-solublepyrophosphate and water-soluble salts of two heavy metals selected tromthe group consisting of iron, cobalt, and nickel.

3. The process which comprises polymerizing an organic compoundcontaining the CHa=C group and which is capable of being polymerized bya peroxide catalyst, in aqueous emulsion in the presence of anaryl(dialkyl)methyl hydroperoxide in which each alkyl group contains notmore than 4 carbon atoms, and an activator comprising a water-solublepyrophosphate and watersoluble salts of iron and cobalt.

4. The process which comprises polymerizing an organic compoundcontaining the CH=C group and which is capable of being polymerized by aperoxide catalyst, in aqueous emulsion in 'the presence of anaryl(dialkyl)methyl hydroperoxide in which each alkyl group contains notan organic compound containing the CHC group and which is capable ofbeing polymerized by a peroxide catalyst, in aqueous emulsion in thepresence of e,a-dimethyl-p-isopropylbenzyl hydroperoxide. I

8. The process which comprises polymerizing butadiene-1,3 in aqueousemulsion in the presence of a,a-dimethyl-p-methylbenzyl hydroperoxide.

7 UNITED STATES PATENTS Number Name Date 2,366,328 Fryling Jan. 2, 19452,367,805 semple Jan. 23, 1945 2,384,574 Stewart et al. Sept. 11, 19452,388,477 Fryling Nov. 6, 1945' 2,388,514 Zeicker et a1 Nov. 6, 19452,395,523 Vaughn et al Feb. 26, 1946 2,400,041 Dickey May 7, 19462,427,847 Fryling Sept. 23, 1947 V FOREIGN PATENTS Number Country Date610,293 Great Britain Oct. 12, 1948 9. The process which comprisescopolymerizing butsdiene-1,3 and styrene in aqueous emulsion in thepresence of o,o-dimethyl-p-isopropylbenzyl hydroperoxide.

10. The process which comprises'copolymerizing butadiene-1,3 andacrylonitrile in aqueous emulsion in the presence 01 e,c-dimethylbenzylhydroperoxide.

11. The process which comprises copolymerizing butadiene-1,3 and styrenein aqueous emulsion in the presence of a,-dimethyl-p-isopropylbenzylhydroperoxide, and an activator comprising sodium pyrophosphate, ferricsulfate, and cobaltous chloride.

12. The process which comprises polymerizing an organic compoundcontaining the CH2=C group and which is capable of being polymerized bya peroxide catalyst, in aqueous emulsion in the presence of anaryl(dialkyl)methyl hydroperoxide in which each alkyl group contains notmore than 4 carbon atoms, and an activator comprising a water-solublepyrophosphate and a water-soluble salt of a heavy metal selected fromthe group consisting of iron, cobalt, and nickel.

;- EUGENE J. LORAND.

REFERENCES CITED The following references are of record in the file ofthis patent:

1. THE PROCESS WHICH COMPRISES POLYMERIZING AN ORGANIC COMPOUNDCONTAINING THE CH2=C< GROUP AND WHICH IS CAPABLE OF BEING POLYMERIZED BYA PEROXIDE CATALYST, IN AQUEOUS EMULSION IN THE PRESENCE OF ANARYL(DIALKYL) METHYL HYDROPEROXIDE IN WHICH EACH ALKYL GROUP CONTAINSNOT MORE THAN 4 CARBON ATOMS.